1. Field of the Invention
The present invention relates to concrete wall casting techniques utilizing pairs of spaced-apart shaping forms held in position by horizontal and vertical supports, the concrete being poured between the forms and on top of the section of wall poured earlier which has become at least partially set. After the most recently poured concrete partially sets, the forms are removed and relocated above the former position. The procedure is repeated until the wall is completed. More particularly, the present invention relates to improved movable supports for concrete shaping forms and apparatus for moving them which are adapted for forming small diameter columns.
2. Brief Description of the Prior Art
Related subject matter is disclosed and claimed in U.S. Pat. No. 3,779,678, issued Dec. 18, 1973, and U.S. Pat. No. 4,040,774, issued Aug. 9, 1977, both to the same inventor as the present invention. The above patents disclose techniques for constructing concrete chimneys, cooling towers and other columns having large diameters, typically in the range of greater than about sixty feet. Such techniques require the use of several heavy framing members on both sides of the concrete wall to accommodate the heavy loads created by the unset, plastic concrete.
The prior art jump-form chimney construction technique uses steel forms that are raised in increments of several feet for each pour. The forms are raised by a crew of workers using chain falls connected to overhead beams on a derrick, which is a structure that incorporates a work deck and is hung by cables from the inside of the concrete column. For each new pour, the derrick is raised using chain falls and reattached by cables to the concrete structure. Then the outside forms are raised, as one piece. Reinforcing steel is secured and the inside forms are raised, again as one piece. After alignment and plumb are checked, the concrete is poured. Taper and wall thickness are adjusted by changing the circumference of the forms.
The prior art slip-form chimney construction technique provides a method for constructing a concrete column monolithically. During construction, concrete is poured continuously into about four-foot-high forms that are steadily raised or "slipped" up the concrete structure using hydraulic jacks. The steady upward progress of the forms is timed so that the concrete is cured before the bottom of the form slips by. This method of construction is well suited for projects where time is of critical importance. It also has proved economical for structures of large diameters and for chimneys of extreme height. However, prior art slip forming techniques also involve very heavy and bulky form structures.
The large size and weight of the shaping forms and their support structure utilized in the foregoing techinques make them unsuitable for casting smaller towers having diameters of about 5 to 30 feet. In addition, the prior art techniques do not include any forming apparatus for casting in place an inner, acid-resistant refractory lining for the column at the same time the concrete column wall is being poured.
An object of the present invention is to eliminate the need for pairs of heavy frame members (one on each side of the wall) to transfer loads created by plastic concrete by replacing them with an inner frame with multiple central stiffeners. It is also an object of this invention to use a novel system of supports which moves the frame and forms into place by hydraulic jacks. A further object of this invention is to provide shaping forms and support structure for casting in place a refractory lining on the inside of the concrete column wall at the same time the column wall is being poured. It is a further object of an alternative embodiment of the present invention to provide an apparatus for using precast refractory panels as the inside shaping form for the concrete wall. Finally, it is an object of another alternative embodiment of this invention to provide a work platform for installation of an inner refractory lining after the concrete wall has been poured.